Variable or constant speed rotating equipment, particularly equipment exposed to hostile environments and cycling or impulse loads, have heretofore not been able to benefit from bearing supports which can statically and dynamically compensate for impending rotor motion leading to rubbing of rotating and stationary parts. Further, those impulses which provide intermittent or constant loads on the bearing supports and other anomalous loadings such as bearing loading due to forces imposed by movement of the axis of rotation cannot be addressed by a "slowly responding" bearing.
While most bearings rely on a thin film of lubricant between rotating elements such as a ball bearing assembly, hydrodynamic bearings and magnetic bearings, some attempts have been made to allow shafts to be supported exclusively by hydrostatic fluid force.
The following prior art reflects the state of the art of which applicant is aware and is included herewith to discharge applicant's acknowledged duty to disclose relevant prior art. It is stipulated, however, that none of these references teach singly nor render obvious when considered in any conceivable combination the nexus of the instant invention as disclosed in greater detail hereinafter and as particularly claimed.
______________________________________ PATENT NO. ISSUE DATE INVENTOR ______________________________________ U.S. PATENT DOCUMENTS 2,459,826 January 25, 1949 Martellotti 2,578,712 December 18, 1951 Martellotti 2,578,713 December 18, 1951 Martellotti 2,692,803 October 26, 1954 Gerard 2,879,113 March 24, 1959 DeHart 2,938,756 May 31, 1960 Loeb 3,053,589 September 11, 1962 Cameron 3,271,086 September 6, 1966 Deffrenne 3,357,759 December 12, 1967 Stephenson 3,395,952 August 6, 1968 Deffrenne 3,403,948 October 1, 1968 Deffrenne 3,432,213 March 11, 1969 Adams 3,442,560 May 6, 1969 De Gast 3,588,202 June 28, 1971 Johnson 3,617,102 November 2, 1971 Wada, et al. 3,658,393 April 25, 1972 Luthi 3,742,653 July 3, 1973 Kano, et al. 3,749,456 July 31, 1973 Whitaker 4,035,037 July 12, 1977 Cunningham 4,193,644 March 18, 1980 Miyashita, et al. 4,215,903 August 5, 1980 Andrews 4,327,592 May 4, 1982 Fincke 4,351,574 September 28, 1982 Furukawa, et al. 4,504,048 March 12, 1985 Shiba, et al. 4,512,671 August 23, 1985 Giers, et al. 4,569,562 February 11, 1986 Sato, et al. 4,630,942 December 23, 1986 Tsumaki, et al. 4,643,592 February 17, 1987 Lewis, et al. 4,650,123 March 17, 1987 Ooishi 4,685,813 August 11, 1987 Moog 4,696,585 September 29, 1987 Swearingen 4,704,879 November 10, 1987 Christ, et al. 4,767,223 August 30, 1988 Goodwin 4,834,559 May 30, 1989 Kalvoda 4,944,609 July 31, 1990 Salter, Jr., et al. 4,947,639 August 14, 1990 Hibner, et al. 5,033,317 July 23, 1991 Van Haag 5,034,639 July 23, 1991 Huss, et al. 5,063,322 November 5, 1991 Sugita, et al. 5,064,297 November 12, 1991 Tanaka, et al. 5,066,197 November 19, 1991 Champagne 5,099,966 March 31, 1992 Wohrl 5,104,237 April 14, 1992 Slocum 5,121,341 June 9, 1992 McCabria, et al. 5,149,206 September 22, 1992 Bobo 5,197,807 March 30, 1993 Kuznar 5,201,585 April 13, 1993 Gans, et al. 5,203,762 April 20, 1993 Cooperstein 5,219,447 June 15, 1993 Arvidsson 5,238,308 August 24, 1993 Lang, et al. 5,281,032 January 25, 1994 Slocum 5,344,239 September 6, 1994 Stallone, et al. 5,356,225 October 18, 1994 Hanes, et al. 5,360,273 November 1, 1994 Buckmann 5,364,190 November 15, 1994 Ochiai, et al. 5,374,129 December 20, 1994 Vohr, et al. 5,391,002 February 21, 1995 Eigenbrod 5,447,375 September 5, 1995 Ochiai, et al. 5,484,208 January 16, 1996 Kane, et al. FOREIGN PATENT DOCUMENTS GB 2,121,892 January 4, 1984 Mohsin JP 0045110 May 3, 1986 Nippon Seiko K.K. ______________________________________
The patent to Cunningham, U.S. Pat. No. 4,035,037, issued Jul. 12, 1977, teaches a hydrostatic bearing support in which a plurality of pressure plates coact with a housing which has a central bore adapted to receive a rotor and a conventional bearing assembly therebetween. This device uses a fluid film bearing, but unlike the instant invention cannot cause the fluid adjacent the rotor to directly change its force profile to provide centered support for the rotor.
Goodwin, U.S. Pat. No. 4,767,223, issued Aug. 30, 1988, teaches the use of a hydrodynamic journal bearing in which an undriven accumulator attempts to respond to changes occurring within clearance that exists between a journal and its circumscribing bearing bush.
Kano, et al., U.S. Pat. No. 3,742,653, issued Jul. 3, 1973 teaches the use of a control device for the radial displacement of shafts in which an upper and front pocket and a rear and lower pocket surround the shaft and a control valve provides pressurized fluid to the upper and front pockets and to the rear and lower pockets respectively to radially displace the axis of the shaft. Because the purpose for this device is to control the feed for a grinding wheel to provide full automation during a grinding cycle, the cycle reflects predictable force profiles.
The patent to Miyashita, et al., U.S. Pat. No. 4,193,644, issued Mar. 18, 1980 teaches the use of a servo control system to position a hydrostatically supported member such as the table of a machine tool or a rotary shaft in which a closed loop control system includes a differential amplifier for effecting a subtraction operation between the amount of displacement of a member and an amount of reference signal. A servo amplifier delivers a control signal while a servovalve supplies operating pressure upon receipt of the control signal to the member.
All of the foregoing patents specifically discussed and those which were cited to show the state of the art further fail to provide substantially instantaneous response to shaft perturbations which cause resonant frequencies and vibration and which drive the shaft from a pure center rotation. A further problem the prior art fails to resolve is that because incompressible fluid theoretically provides a desirable cushion between a rotating member and its stationary support, incompressible fluids also have an inherent lag in the ability to respond to dynamic changes, particularly sudden unexpected loads and high speed fluctuations.